1. Field of the Invention
The invention concerns a device and a method to transfer product stacks.
2. Description of the Prior Art
The manufacturing of plastic containers (such as bowls, covers and shells) normally ensues in a machine cycle in a two-dimensional pattern or a product matrix. The products produced in a machine cycle can then be inserted into stacking shafts. The manufacturing of the next product series subsequently ensues in a product matrix. These products are also again inserted into the stacking shaft etc. until these are filled. Such a stacking shaft is normally a very simple bar stock carrier. The stack formation can ensue either horizontally, at an angle or vertically. The stack is discharged via a lifter mechanism or a blade and passed to a worker for further relaying. In the next work step, the product stack is either packaged directly in a carton or supplied beforehand to a shrink-wrapping machine to wrap the individual product stacks in film, and is subsequently packaged in a box.
The action of the packing and repacking the product stack presently normally ensues by hand. In particular if the product stack is shifted into horizontal stack magazines, such as by means of a blade, it can occur that the product stack falls apart, such that in addition to handling the stack a worker must first correct this. Because the product stack is discharged and additionally processed or packaged by hand, the maximum stack height is limited since otherwise the danger exists of such a product stack breaking apart. The same problem also occurs in vertical stack cages. Here the stack is transferred row by row or block by block onto a conveyer belt via a separate lifter mechanism after reaching a specific stack quantity. Here as well, there is a risk that the stacks will fall apart. The conveyer belt additionally serves as a buffer storage. After discharging the stacks, these are supplied to a packing machine that shrink-wraps the individual product stacks with a film. The wrapped product stacks are then likewise manually packaged.
It is disadvantageous that the relaying and the packaging of such product stacks cannot ensue in a fully automated manner. The fact that a number of different products for which the shaping, punching and discharging tools are to be refitted are produced on such shaping machines also contributes to this disadvantage.
Although it is already known to transfer product stacks vertically from a stack magazine into a rigid receptacle in the form of an external stack cage or grabber (WO 2005/061353 A2, WO 2006/027053 A1), a flexible, fully automatic additional processing of product stacks in the aforementioned sense is still not also possible with this.